Method of making asphalt emulsions



Patented May 28, 1929.

UNITED STATES PATENT OFFICE.

ARTHUR L. HALVORSEN, OF PERTH .AMZBOY, AND PIERCE M. TRAVIS, OF RIDGEWOOD, NEW JERSEY, ASSIGNORS TO THE EMULSION PROCESS CORPORATION, OF JERSEY CITY, NEW JERSEY, ACORPORATION OF DELAWARE.

METHOD OF MAKING ASPHALT EMULSION S.

No Drawing.

This invention relates to asphalt emulsions and has for its objects the provision of certain improvements in the manufacture of asphalt emulsions.

The asphalt emulsions of commerce are for the most part mixtures of asphalt and water with various agents designedto effect and maintain an emulsification of the asphalt and water. Colloidal clays have been largely used commercially as so-called emulsifying agents, while numerous other substances have been suggested in the patent and other literature, such for example as colloidal vegetable and animal substances, soaps, alkalies, etc., which are true emulsifying agents. Relatively large amounts of these agents have been prescribed as necessary in order to produce a reasonably stable asphalt and Water emulsion, and/or suspensions in the case of clays and the like.

WVe have discovered that tri-sodium phos phate crystalline (Na .PO +12I-I O), or dehydrated tri-sodium phosphate (Na POQ in relatively small amounts eflects-very satisfactory and true emulsification of asphalt and water. \Ve have moreover found that this emulsifying action is only effective when limited quantities of tri-sodium phosphate are used. In other words, there appears to be a critical relationship between theamount of tri-sodium phosphate used and the effectiveness of the emulsification, whereby satisfactory emulsification can only be obtained when the amount of tri-soduim phosphate employed is between critical predetermined limits, which vary with different kinds of asphalts. Thus, when the amount of tri-sodium phosphate employed as the emulsifying agent is increased beyond about 0.4% Na PQ, calculated by weight with respect to the emulsion in the case of a certain grade of Bermudez asphalt, the resulting mixture of asphalt and water While possessing certain aspects of an emulsion is a markedly inferior product to that obtained when less than 0.4% or about 0.24%: of Na 'PO, is employed as the emulsifying agent. While with a California steam distilled asphaltic base oil residual asphalt the best emulsion is obtained when using more than 0.4% but less than 0.6% Na PO Our present invention, based on the foregoing discoveries, involves the emulsi'fication Serial No. 258,992.

of asphalt and water by the emulsifying action of relatively small amounts of trisodium phosphate, preferably not exceeding 0.24% Na PO by weight on the weight of the finished emulsion, in some cases. In the practice of the invention We have secured excellent results with from 0.1 to 0.3%. of Na PO,, calculated by weight with respect to the Weight of the emulsion. In no case should the tri-sodium phosphate exceed about 0.7 5% Na PO by weight on the emulsion, and the optimum results will usually be obtained when the amount of tri-sodium phosphate is considerably less than 0.6%.

The following examples illustrate the practical application of the principles of the invention:

100 kilograms of Water are heated approximately to boiling, as for example by the injection of live steam. One kilogram of crystalline tri-sodium phosphate equal to about 0.4 kg. Na PO is added to this hot Water. 100 kilograms of freely flowing molten asphalt are then gradually run into the hot water containing the dissolved trisodium phosphate. The mixture is vigorously stirred while the molten asphalt i being added to the water. The stirrer used ly and uniformly dispersedthroughout the water, the mixture is run through an emulsifying machine, such. for example, as a colloid mill. The resulting emulsion discharged from the emulsifying machine is relatively hot and while cooling to room temperature should be gently stirred, with or without artificial cooling.

a As another example of the application of the invention, we will describe the manufacture of an emulsion containing three parts of asphalt and one partof Water. The water (250 kilo-grams) containing four (4) kilograms of crystalline tri-sodium phosphate (1.6 kg. Na PO,) is heated to a temperature of about 80 C. The molten asphalt (750 kilograms) at about 135 C. is introduced into the water in a regulated stream loid mill, from which the finished fine emulsion is continuously discharged. The'emulsion discharged from the emulsifier is cooled, artificially if desired, with gentle stirring and canned, or otherwise prepared for storage or use. The operations of cooling and canning are preferably conducted in a con-. tinuous manner to prevent asphalt skin formation caused by undue exposure of the warm and rich emulsion to air.

, The cold emulsion resulting from the foregoingvoperation is of 'a dark. brown color. and of a heavy consistency but will yet flow which is remarkable considering the high asphalt content (3 asphalt to 1 water) and the small amount of emulsifying agent (1.6 parts Na PQ to 750 parts asphalt or 1000 parts emulsion). Theemulsion, while very stable in the cans, reforms true asphalt in a very few minutes when coated on a concrete wall, cardboard, metal, etc; the coating being just as water-proof, black and shining as when formed from non-emulsified asphalt. The concentrated emulsion may, if desired, be thinned with water to form a more dilute emulsion. For example, two parts of the emulsion may be mixed with one" part of water to make a thin brown emulsion of milk-like consistency containing about 50% pure asphalt.

As a third example of the application of the invention, we will describe the manufacture of an emulsion containing 60% asphalt and made from a California steam distilled asphaltic base oil residual asphalt. The water (67 kilograms) containing 1 kilogram Na PO is heated to a temperature of about 90 C. The molten asphalt (100 kilograms) at about 150 C. is introduced into the water in a regulated stream and with continuous agitatlon from a fast moving propeller agitat'or. The emulsion discharged from the emulsifier is cooled very quickly by artificial prepared for 0.3 kilograms N a PO is heated to'a temperature of about 90 C. The molten .asphalt (100 kilograms) at about 150 is introduced into the water in a regulated stream and with continuous agitation from a fast movingpropeller agitator. The emulsion discharged from the emulsifier is cooled very quickly by artificialmeans and'canned or otherwise prepared for storage -'or use. It has also been found that even smaller amounts of tri-sodium phosphate may be advantageously employe V Vhile the invention is of general application and can be advantageously practiced with substantially all asphaltic materials, it is particularlyapplicable in preparing emulsions of asphalts containing relatively small percentagesof mineral matter. Thus, for example, natural or residual Bermudez asphalts, California or similar asphaltic base oil residue asphalts, orcut-back asphalt cements thereof, containing around '1 to 7% of mineral matter are admirably suited for the practice of the invention. Similarly, the residual asphalts from the distillation of other asphaltic base oil, or cut-back asphalt cements thereof, are well suited for the practice of the invention. Emulsions made of such asphalts contain relatively small amounts of mineral or similar inert matter, and consequently contain maximum percentages of the desirable hydrocarbon compounds of. asphaltie materials. Moreover, in consequence of the small amount of trisodium phosphate used, the emulsions are not contaminated with any substantial quan tity of emulsifying agents.

The melting point of the asphalt used in practicing the invention should not be substantially higher than the boiling temperature of water, since otherwise objectionable steaming of the water will take place upon mixing the water and molten asphalt. Since the melting point of asphalt is to some extent dependent upon its hardness, as determined by its penetration factor, it follows that in general it is desirable to use asphalts of relatively high penetration factors. Where the penetration factor is too low, the asphalt may be cut-back with hydrocarbon oils,

thereby producing what is known as asphalt cement, to appropriately increase its penetration factor. We have secured excellent results in the practice of the invention using Bermudez asphalt products having a penetration factor of 80 and upwards at 25 C., as determined by the Dow penetrometer and with the aforementioned California asphaltic base oil residue asphalts having a pene-- tration factor of 70.

The asphalt emulsions of the invention. are characterized by their relatively low viscosity, considering their high asphaltic contents.

Thus, the emulsions of the invention are freely flowing liquids, as contrasted with the paste-like products of equivalent asphalt content that have heretofore appeared on the market. Moreover, the products of the inmicroscope, the emulsions of the invention are seen to consist of minute globulesof asphalt very uniformly distributed throughout the Water, which constitutes the continuous or external phase of the emulsion.

The emulsions of the invention are moreover characterized by their brown color, thereby further evidencing the very fine state of subdivision of the black dispersed phase (asphalt). The color of an asphaltwater emulsion becomes lighter'(i. e., varying from blackdo brown) as the asphaltbecomes more finely subdivided and dispersed in the water. This is believed to be due to the increased reflection and scattering of light in consequence of the increased subdivision and dispersionof the asphalt particles. This color phenomenon is utilized in the preparation of the emulsions, and the operator judges the completeness of the dissemination. of the asphalt throughout the water and hence the desired end-point in the mixing and/or emulsifying operations by the brown color of the resulting product.

The emulsions of-the invention are furthermore characterized by their relatively rapid drying qualities, that is, their ability,

upon application in the form ofa thin coating, to set or reform within a few minutes into an impermeable coalescent coating of true pure asphalt, typified by its shining black appearance. WVhen applied to a surface with a spray-gun, the asphalt dries and sets almost immediately, and when applied by a brush or the like, dries and sets in a very few minutes. The drying and setting of the asphalt is more rapid, the more porous the material to which the emulsion is applied. This rapid drying quality of the emulsion of the invention is due, we be lieve, to the high degree of subdivision and dissemination of the asphalt, whereby greatly increased surface areas are exposed for evaporation of the water.

The emulsions of the invention, when .applied and dried, produce an asphalt coat ing of characteristic black and glossy appearance. that the coating consists of pure asphalt uncontaminated with any substantial amounts of emulsifying agents or other inert substances. This is in striking contrast with the so-called asphalt emulsions containing clay and the like, which when dry have a dull, flat appearance. This absence of any'substantial amount of emulsifying agents or other inert substances in the asphalt coating produced by the emulsions .of the invention, results in securing the maximum efiectiveness of the asphalt as a waterproofing or protective medium. It is to be understood, however, that non- Thisis largely due to the fact.

asphalt.

emulsion breaking fillers may be added where very thick coatings are desired and suitable'fillers giving an initially water permeable characteristic may be used so that the water phase may evaporate or flow off, for if a heavy coating of the pure emulsion be attempted, the outer surface or skin thereof under certain conditions as applied to certain materials would not allow the water to evaporate after such a skin had been formed.

The emulsions of the invention are very stable and have no tendengy to break down on standing. When stored in cans or other receptacles, some slight settling may take place, but the relatively thin layer of super natant liquor is readily mixed in and tlie uniformity of the emulsion reestablished by simply stirring. The emulsions, more particularly those of relatively high asphalt content, can be readily diluted or thinned with water accompanied by appropriate stirring to produce more fluid or less concentrated emulsions, as desired.

We do not desire to be restricted to any theory of the effectiveness of small amounts of tri-sodium phosphate in emulsifying water and asphalts, and the fact remains that small amounts of tri-sodium phosphate produce remarkably effective emulsification of asphalt and water. We believe that the effective-emulsifying action of small amounts of tri-sodium phosphate, characteristic of the present invention, is due in part to the chemical, and perhaps physical, composition and behavior of tri-sodium phosphate, as well as to its presence in amounts preferably not exceeding around 0.6% (Na POQ by weight on the emulsion, and in no case exceeding about 0.75%.

It should be noted that in accordance with our invention, the complete emulsification may be effected with a fraction of one percent (1%) of tri-sodium phosphate. Other agents or substances may, however, be added to the emulsion for imparting thereto qualities or properties quite apart from that of emulsific'ation. In this connection, however, care must be taken not to add substances that exercise a deleterious effect upon or break down the emulsion. In all cases, however, the additive emulsifying agent will not substantially exceed 1.5% and the emulsion will consist principally of water and In their preferred form, employing asphalts of low mineral content, the emulsions of the invention contain by weight over and preferably not less than of combined water and asphaltic constituents soluble in carbon bisulfide.

While we have particularly mentioned trisodium phosphate, other water-soluble alkaline 'phospshates of monovalent metals,

may be employed as the emulsifying agent, and are to be understood as included in the scope of the a pended claims. The relative cheapness an commercial availability of tri-sodium phosphate, however, make it a convenient agent in practice. Also the separate addition of the necessary component metal salts and a phosphoric reagent may under certain conditions be employed.

We claim:

1. The improvement in the manufacture of asphalt-water emulsions which comprises effecting the emulsifieation of the asphalt and water with tri-sodium phosphate in amount not exceeding 0.75% of Na PO by weight on the emulsion.

2. The improvement in the manufacture of asphalt-water emulsions which comprises effecting the emulsification of the asphalt and water with about 0.1 to 0.3% Na PQ by weight on the emulsion.

3. The improvement in the manufacture of asphalt-water emulsions which comprises gradually adding molten asphalt to a body of actively agitated hot water containing tri-sodium phosphate in amount not exceeding 0.3% Na PO by weight on the resulting final emulsion, and continuing the mixing and emulsifying operations until the asphalt is uniformly dispersed throughout the water in the form of minute globules.

4:. The improvement in the manufacture of asphalt-water emulsions which comprises gradually adding not less than one part by weight of molten asphalt to one part by weight of hot water containing tri-sodium phosphate in amount not exceeding 0.3% Na PO by weight on the resulting final emulsion, actively stirring the water and asphalt approximate the point of addition of the asphalt and thereby dispersing the asphalt promptly after its addition, and continuing the mixing and emulsifying operations until the asphalt is uniformly dispersed throughout the water in the form of minute globules.

5. The improvement in the manufacture of asphalt-water emulsions which comprises gradually adding from two to three parts by weight of molten asphalt to one part by weight of a body of actively agitated hot water containing tri-sodium phosphate in amount not exceeding 0.3%

Na PO, by Weight on the resulting final of asphalt-water emlusions-which comprises contacting finely divided asphalt with a -water solution of tri-sodium phosphate, said phosphate being provided in amount not ex- 7 ceeding substantially 0.75% weight on the emulsion.

8. The improvement in the manufactureof asphalt-water emulsions which comprises intimately mixing not less than one part by weight of molten asphalt with one part by weight of a water solution of tri-sodium phosphate, said phosphate being provided in amount not exceeding 0.75% Na PO by weight on the emulsion. g In testimony whereof we aflix our signatures.

ARTHUR L. HALVORSEN. PIERCE M. TRAVIS.

Na PO, by 

